P2855 R1 Member customization points for Senders and Receivers

[brycelelbach]

P2855R0 Member customization points for Senders and Receivers (Ville Voutilainen)

[inbal2l]

2023-06-12 Library Evolution Varna

P2855R0: Member customization points for Senders and Receivers

2023-06-12 Library Evolution Minutes

Chair: Fabio Fracassi, Nevin Liber

Champion: Ville Voutilainen

Minute Taker: Nat Goodspeed

Summary

POLL: We want to spend more time on the direction of P2855 (knowing that our time is limited) and investigate where we can use member functions for S/R customization points.

SF	F	N	A	SA
13	17	4	1	0

Attendance: 31 (P) + 4 (R)

# of Authors: 1

Author's Position: (wasn't recorded)

Outcome: Strong consensus in favor.

Senders/Receivers in its current form uses a powerful/flexible yet syntactically heavy library mechanism for function customization (tag_invoke).
The mechanism is complex enough that consistent employment of might degrade the usage experience of S/R (in terms of readability, ease of use and compile times).
Since the progress of a much needed language mechanism along the lines of [[https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2547r1.html][P2547]] has stalled in EWG, this paper proposes a to use a simpler mechanism.

Outcome

We approve of the general direction of the paper, but need further work on the details e.g.

• which functions should remain tag_invoke (because the flexibility is needed)
• is a tag still useful to not capture terms like start or connect.
• path forward to an potential language feature along the lines of [[https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2547r1.html][P2547]]
• The paper requires wording (against P2300)

[inbal2l]

2023-11-06 Library Evolution Kona

P2855R0: Member customization points for Senders and Receivers

2023-11-06 Library Evolution Minutes

Was seen as a reference to the work done to reduce "tag_invoke". No progress was made on the paper.

[ben-craig]

2024-03-21 Library Evolution Tokyo

P2855R1: Member customization points for Senders and Receivers

2024-03-21 Library Evolution Tokyo Minutes

Champion: Ville Voutillainen
Chair: Ben Craig / Inbal Levi
Minute Taker: Guy Davidson

Summary

POLL: Send P2855R1 (Member customization points for Senders and Receivers) to LWG for C++26 classified as B1, to be merged into P2300, to be confirmed with a Library Evolution electronic poll.

SF	WF	N	WA	SA
12	5	2	0	0

Attendance: 16+5

# of Authors: 1

Author Position: SF

Outcome: Strong Consensus

Comments:
WF: SF if there was more impl experience

POLL: Remove receiver_adaptor ([exec.utils.rcvr.adptr]) and related tag invoke overloads ([exec.utils.rcvr.adptr.nonmembers]) from P2300, pending electronic polling results.

SF	WF	N	WA	SA
15	2	0	0	0

Attendance: 16+5

# of Authors: ???

Author Position:

Outcome: Strong Consensus

Comments:

Next Steps

Electronic polling and merging with P2300.

[inbal2l]

P2855R1 was added to 2024 April LEWG electronic poll paper (P3213R0)